Focus adjuster for enlargers



July 15, 1941. E. c. ROGERS 2,249,229

FOCUS ADJUSTER FOR ENLARGERS Filed Feb. 17. .1940

lMMMMMMEMMMW INVENTOR.

Patented July 15, 1941 UNITED STATES PATENT OFFICE.

FOCUS ADJUSTER FOR ENLARGERS Elwood C. Rogers, Indianapolis, Ind.

Application February 17, 1940, Serial No. 319,420

12 Claims.

My invention relates to focus adjusters for lenses, especially of photographic enlargers, and particularly to focus adjusters intended to be forcused manually by the operator.

In focusing an enlarger, it is necessary for the operator to adjust the focusing mechanism while watching the enlarged image, and to judge by the appearance of such image when the proper focus has been obtained, As the image approaches exact focus, however, the changes produced by further adjustment of the focusing mechanism toward exact focus become so slight that it is difficult for the operator to discern those changes. For final adjustment, therefore, it is usual practice to move the lens back and forth across the point of exact focus to observe the changes thus produced and to judge from those changes where the point of exact focus is, and then to move the lens to the position judged to be the point of exact focus.

It is the object of my invention to provide a focusing mechanism which may be adjusted to bring the lens to approximate focus, and which has an adjusting device particularly suitable for the final focusing operation, and to arrange this latter device so that the final operation may be done rapidly and accurately at any point within a fairly wide range from the setting for approximate focus. It is my further object to provide a focusing mechanism which may be used either for adjusting a lens which is a special lens forming part of a photographic enlarger or for adjusting a lens of a so-called miniature camera which may be mounted in the enlarger to become part thereof if desired. A further object of my invention is to arrange the parts of the adjusting mechanism to secure freedom of movement, especially throughout the final adjustment, and to avoid any tendency for the lenscarrying parts to become misalined during the focusing adjustment.

In accordance with my invention, I may provide an enlarger with a vertically depending stem on which a slide is vertically movable; and this slide carries the lens which is to be adjusted, whether it is a lens specially mounted for use as part of the enlarger or is a lens of a miniature camera which may be mounted on the enlarger. This slide may be given an approximate adjustment upward or downward by a nut on a vertical screw; and may be given a final adjustment upward or downward by a cam member which rests on the nut and which has a helical cam that reacts against the slide, desirably at a point close to the stem on which the slide is movable,

and that may be operated accurately and conveniently by a projecting arm of considerable length.

The accompanying drawing illustrates my invention. In such drawing Fig. 1 is a side elevation of a photographic enlarger equipped with my focus adjuster, with some of the parts in section; Fig. 2 is an enlargement of part of Fig. l,

showing the adjusting mechanism on a larger scale; Fig. 3 is a section on the line 3--3 of Fig. 2; and Fig. 4 is a view similar to Fig. 2 but showing the focusing mechanism in use with the lenscarrying portion of a miniature camera mounted on the enlarger.

The photographic enlarger shown has an upright I0 mounted on a table II and provided with a vertical slideway I2 on which is mounted a main slide member I3 which carries the main body of the enlarger. The slide member I3 may be clamped in any desired place on the slideway I2 by a clamping screw I4. The outer end of the main slide member I3 carries the enlarger casing I5 in which is mounted a lamp bulb I6 and a negative carrier I8, and may carry any suitable condensing lenses I'I. This whole mechanism moves upward and downward with the main slide member I3.

From the lower end of the enlarger casing I5 a camera bellows 20 extends downward, to an adjusting slide 2l which carries the objective lens 22. The adjusting slide 2l is vertically slidable on a stem or rod 23 extending vertically downward from the main slide member I3, and it is desirably pressed downward on that rod 23 by a light spring 24. The adjusting slide 2I is held from turning on the rod 23 by a screw 25 which also extends downward from the main slide member I3 and passes through a hole in the adjusting slide 2I.

Below the adjusting slide 2l, the screw 25 has mounted on it a knurled nut 2E, on which rests a cam member 2l. The cam member 21 has a relatively long laterally extending operating handle 28, which has a considerable leverage so that such handle moves a considerably greater distance than the cam surface of said cam member 2l. The cam member 2l is provided on its upper face with a helical cam surface 29, which extends for something like one-half a turn; and the hub of the adjusting slide 2| rests on this cam surface 29. The pitch of the cam surface is such that the camming mechanism is irreversible, although it is desirably suflicient to give a considerable movement to the hub during movement of the cam member.

In operation, the approximate adjustment or the adjusting slide 2i, and therefore or the objective lens E2, is obtained by adjusting the knurled nut which by its rotation, and its consequent travel along 'he so 1ew E5 to a desired position locates th cam 2" bodily at a desired point on that scr .v 25, and thus locates the adjusting slide il which rests on tne cam surface The nut is desirably relatively large and heavy, so that practice the adjusting slide 2i and cam nember El may be lifted and the nut ES spun to cause it to rapidly travel either' upward or downward on the screw 25 to approximately tie desired position for focus of the objective lens. The slide El and cam member El are tl rested on the nut 2t and the final adjustment may be obtained by manipulating the handle to raise and lower the hub oi the adjusting slide 2i quickly and under accurate control. The spring 24 assists gravity in keeping the hub of the adjusting slide 2l seated on the cam surface EG; and the cam surface reacts directly on the hub close to the rod 23 so that its reaction llas no eiective tendency to cool; the slide on the rod or rotate the slide about the rod.

In the construction which has just been described, the bellows 2G is permanently attached at its upper end to tlie enlarger casing l5 and at its lower end to the adjusting slide 2l and the lens 22 is mounted in that edjusti g sli le.

However, if desired, the adjusting slile ay made with a forked end 2id, to adapt to su port the lens-carrying portion of iiniature camera.

One form of miniatunc camera has a case which is open at the back, a removable basl; for closing the case, and an extensible lens carrier spring pressed to extended position. The lens is mounted in a sleeve projecting forward from a collar at the iront of the lens carrier The folzed end Zia is adapted to nt around he sleeve of the lens 22a of the miniature camera and to bear against its surrounding collar. The adjusting slide with the forlred end Ela may thus be used to hold tbe camera case 3@ upwardly against tne lower face of the enlarger casing l5, by moving the slide upwardly against the collar to within the range of extension of the cali-- era lens-carrier. The lens 22a is then held in position to act as tbe objective lens of the/n enlarger, and may be adjusted for focus by movement of the adjusting slide within the range of compression and extension of the spring-pressed lenscarrier.

The adjustment of tbe adjusting slide with the forked end Eid is accomplished in the same way as the adjustment already described for adjusting the adjusting slide 2 l, by manipulation of the nut and the cam El.

I clairi as my invention:

l. A focus adjuster for photographic cnlargers. comprising, in combination with the enlarger casing, an ble nwmber movable with respect to casing and controlling the po 'ion oi the objective lens of the enlarger relatively to the casing. adjusting for said member, and a cam member interposed between said adjustmg means and said member movable to adjust said member with respect to s .c adjustoY the o the casing, adjustng means o aid member, and

yeen said adjusting means and said member and movable about a paralleL with tno axis ci the objective lens to adjust said member with respect to said ading means.

3. A focus adjuster for comprising, in combination with the enlarger casing, an adjustable s movable v ith respect to cas ig and controlling the position of the objective lons of the enlarger relatively to the casing, sming means urging the slide in one direction relative to the casing, an adjusting device a"fiistably movable in a direction parallel to the direction of movement or said slide, and a cam member supported against said adjusting device and reacting against said slide in opposition to said spring means, and means for moving said cam member to adjust said slide through a limited range with respect to said adjusting device.

ll. A focus adjuster as donned in claim l, with thc additio or a liandle b which the cam member is movable ant which has a considerable 1everage on said cam.

5. A focus adjuster as defined in claim 3, with the addition of a handle by which the cam member is movable and which has a considerable leverage on said cam member.

S. A locus adjuster for photogra com in combination v.

Caf`11 runs,

hic enlargers, -th the enlarger a depending rod fixed with relation to said Casin an adjusting slide vertically movable on such rod and controlling the position of th objective lens of the enlarger, a second rod fixed with relation to said casing and parallel with first rod and guiding said slide against rotation about said first rod, an adjusting device associated with said second rod for adjusting the position of said slide, and a cam member interposed between said adjustinfr device an said slide and movable to adjust tbe slide with rcspect to said device.

7. A focus adjuster for photographic enlargers, comprising, in combination with the enlarger casing, a rod fixed with relation to said casing, an adjusting slide movable on such rod and controlling the position of the objective lens of the enlarger, a spring on said rod and tending to move said adjusting slide along said rod, a second rod fixed with relation to said casing and parallel with said ilrst rod and guiding said slide against rotation about said first rod, an adjusting device associated with said second rod for adjusting the position o said slide, and a cam member interposed between said adjusting device and said slide and movable to adjust the slide with respect to said device, said cam member being arranged to act against said slide at a point close to said rst rod whereby the action of said cam member is substantially directly opposed to the action of said spring.

8. A focus adjuster for photographic enlargers,

' comprising, in combination with the enlarger casing, a rod fixed with relation to said casing, adjusting slide movable on such rod and controlling the position of the objective lens of the enlarger, a spring tendiniT to move said adjusting slide along said rod, a screw mechanism having a member movable with respect to said rod, and a cam member mounted on said movable member of screw mechanism and engaging said adjusting slide and movable to obtain rapid and accurately controlled adjustments of said adjusting slide with respect to said mevable member.

9. A focus adjuster for photographic enlargers, comprising, in combination With the enlarger casing, a depending rod fixed with relation to said casing, an adjusting slide vertically movable on such rod and controlling the position oi the objective lens of the enlarger, a screw mech anism having a member vertically movable with respect to said rod, and a cam member mounted on said vertically movable member of said screw mechanism and engaging said adjusting slide and movable to obtain rapid and accurately controlled adjustments of said adjusting slide with respect to said vertically movable member.

10. A focus adjuster for photographie largers, comprising, in combination with the enlarger casing, a depending rod fixed with relation to said casing, an adjusting slide vertically movable on such rod and controlling the position of the objective lens of the enlarger, a screw mechanism having a member vertically movable with respect to said rod, and a cam member mounted on said vertically movable member of said screw mechanism and engaging said adjusting slide and movable to obtain rapid and accurately controlled adjustments of said adjusting slide with respect to said vertically movable member, the cam surface of said cam being in the form of a helix.

ll. A focus adjuster as denned in claim 9 with the addition of a handle by which the cam member is movable and which has a considerable leverage on said cam-member.

12. A focus adjuster for photographic enlargm ers, comprising in combination with the enlarger casing, a lens-carrier supporting the objective lens of the enlarger and movable toward and away from the enlarger casing, a reaetion inember, a cam member operable between said lens-- carrier and said reaction member to move said lens carrier through a limited range of adjust-A ment relatively to the reaction member, means for adjusting the reaction member toward and away from the enlarger casing, and an operating handle for said cam member and having a conu siderable leverage on said cam member.

ELWOOD C. ROGERS. 

